diff --git a/CMakeLists.txt b/CMakeLists.txt
index 244384fb9a..afd2ff7d90 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -2260,6 +2260,9 @@ if(NOT CURL_DISABLE_INSTALL)
   endforeach()
 
   foreach(_libdir IN LISTS _custom_libdirs CURL_LIBDIRS)
+    if(NOT CMAKE_VERSION VERSION_LESS 3.20)
+      cmake_path(SET _libdir NORMALIZE "${_libdir}")
+    endif()
     list(FIND _sys_libdirs "${_libdir}" _libdir_index)
     if(_libdir_index LESS 0)
       list(APPEND _ldflags "-L${_libdir}")
@@ -2294,6 +2297,9 @@ if(NOT CURL_DISABLE_INSTALL)
       get_filename_component(_libdir ${_lib} DIRECTORY)
       get_filename_component(_libname ${_lib} NAME_WE)
       if(_libname MATCHES "^lib")
+        if(NOT CMAKE_VERSION VERSION_LESS 3.20)
+          cmake_path(SET _libdir NORMALIZE "${_libdir}")
+        endif()
         list(FIND _sys_libdirs "${_libdir}" _libdir_index)
         if(_libdir_index LESS 0)
           list(APPEND _ldflags "-L${_libdir}")